In many cases, an installation place of a motor in a substrate processing apparatus which performs polishing or cleaning of a substrate (e.g., a semiconductor wafer) has a sealed structure in consideration of waterproofness.
For example, in a substrate cleaning apparatus for scrub-cleaning a surface of a substrate with a roll cleaning member, the cleaning is performed by rotatably driving a cleaning member called a cleaning rotating body provided with cleaning rolls and a cleaning sheet by a driving force of a motor (an electric motor), and pushing the cleaning member against the surface of the substrate (see, e.g., Japanese Laid-Open Patent Publication Nos. 2002-066899, 2002-066466, and 08-243511). In many cases, the motor for rotatably driving the cleaning member is provided inside, for example, a housing having the sealed structure in consideration of the waterproofness.
In general, cooling heat generated by the driving of the motor provided in the installation place with the sealed structure is performed by radiation-cooling that spontaneously radiates the heat to components or a space (air) around the motor.